In recent years, driving aid arrangements such as autonomous cruise control arrangements (ACC), also called adaptive cruise control, have been developed in the automotive industry. An autonomous cruise control is a cruise control system for road vehicles that controls vehicle velocity and automatically adjusts the vehicle velocity to maintain a safe distance to preceding vehicles. In addition, semi-autonomous systems are available at the market which are capable of controlling steering, propulsion unit and wheel brakes of vehicles. In addition, fully-autonomous systems are under development which are capable of a full control of steering, propulsion unit and wheel brakes of vehicles to guide a vehicle along a route without intervention of a driver. Control in all these systems is usually based on sensor information from on-board sensors arranged to monitor a driving environment surrounding the vehicle. Such monitoring can be performed with good reliability by means of sensor arrangements such as RADAR (Radio Detection and Ranging) sensors and/or LASER (Light Amplification by Stimulated Emission of Radiation) sensors, and/or LIDAR (Light Detection and Ranging) sensors, and/or imaging sensors.
However, to perform a safe control of vehicle velocity, one must also have knowledge about a current tire to road friction. During travel, estimating a current tire to road friction is an inherently difficult task. Many methods and sensor arrangements have been developed for the purpose. Almost all of these methods and sensor arrangements have in common that they will not always be able to provide a tire to road friction estimate or will not always be able to provide a reliable tire to road friction estimate. In fact, during normal driving, these methods and sensor arrangements will most often not be able to provide a tire to road friction estimate, or at least not be able to provide a reliable tire to road friction estimate. When a reliable tire to road friction estimate cannot be provided, currently available driving aid arrangements usually assume a low tire to road friction, corresponding to a worst-case tire to road friction, and perform control of host vehicle velocity in dependence thereof.
A problem of the assumption of a low worst-case tire to road friction is that it results in greater distances to preceding vehicles and lower velocities of host vehicles, even in situations where the actual tire to road friction is significantly higher than the assumed worst-case tire to road friction, which most often is the case.